Print monitoring systems are commonly used to monitor printed matter in some types of paper/sheet handling systems and to make certain control decisions based upon the character of the printed matter. The following is a list of a few common applications:
1. Print quality monitoring: The monitoring system detects the precision with which the printing system has formed the printed matter and/or the consistency with which the matter is printed across the entire paper. For example, in a laser printing system, the monitoring systems detect low-toner situations where the contrast of the printed matter has degraded unacceptably.
2. Digit control: Overnight package delivery systems, for example, typically use preprinted multi-layered shipping receipts that are filled out by the customer; the customer keeps one receipt, the package recipient receives a receipt with the package, and then typically, a few receipts are retained for the carrier's records.
Such receipt systems are typically printed with a package tracking number that is represented as an alpha-numeric sequence on the customer's and recipient's copies and encoded in a universal product code (UPC) or bar code symbol on at least one of the carrier's receipts. The carrier's package tracking system is based upon the presumption that the package tracking numbers are the same for each layer of the receipt. In such situations, print monitoring systems ensure that the package tracking numbers of each layer match during assembly of the receipt.
3. Sequence control: When mailing personalized advertisement materials and in all cases when mailing bills, it is necessary to ensure that all pages of the mailing insert are combined into the proper envelope. This is especially important in the case of confidential information, such as credit card or phone bills. Even if sheet transfer and handling error rates are low, the risk that a wrong bill will be sent to a customer is unacceptable thus requiring checking each page and the envelope prior to insertion.
Historically, sequence control has involved closely monitoring the printers, feeders, cutters, folders/accumulators, inserters, and stackers for paper jams or other error conditions. With proper coordination, the right materials generated by the printers can be placed into the correct envelopes or accumulated into the proper packets or publications.
Especially in the case of mailing sensitive material, print monitoring systems have been developed more recently to confirm the printed material contents prior to placement in an envelope. To enable monitoring, sequence control information is commonly placed into the printed matter, or implicit in it. For example, checks have separate identification numbers, bills have the customer account numbers at a predetermined locations. The print monitoring system can detect these identifiers and use them as sequence control information to ensure that all pages of a given bill for a account number are placed in the proper envelope and addressed to the proper customer and avoiding the inclusion of any extraneous bill pages.
More recently, with the introduction of production speed, low cost laser printing machines, mailed marketing material, brochures, and other materials have been personalized for a specific recipient, even in high volume printing jobs. In these cases, sequence control issues are important, and in many cases can be similarly critical due to confidentiality concerns and embarrassment caused by unintended recipients. Unfortunately, in this environment, the inclusion of explicit sequence control information on the printed matter is many times unacceptable. Formal letters and brochures will typically not include machine readable information at predicable locations to enable the print monitoring system to ensure that proper sequencing is being maintained.
Attempts have been made at placing non-intrusive information into printed matter. Glyph codes are one example. Information is typically encoded into glyph codes by modulating the orientation of optically detectable symbols or glyphs. Using such techniques, large amounts of information can be encoded into printed images for copy control or copyright tracking, for example.